Vehicle-Trailer Resistance Estimation Using Coast-Down Data
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Solution Overview
Problem
The resistance force characteristics of a vehicle with an attached trailer are unique and unknown, leading to errors in driving range, energy economy, and brake settings, as existing technologies fail to accurately determine these forces for each vehicle-trailer combination.
Innovation Solution
A system using coast-down data to compute constants representing aerodynamic and rolling resistance of a vehicle and trailer, which are then used to control vehicle functions and determine parameters such as combined weight and trailer brake gain settings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If generic resistance force constants are used for vehicle-trailer combinations, then device complexity is reduced, but measurement precision and reliability of range estimates, energy economy, and brake settings deteriorate
Solution Approach 1:
The system performs preliminary coast-down tests to determine resistance force constants before normal operation. These tests are conducted in advance to establish accurate vehicle-specific constants (C1, C2) that account for the unique aerodynamic and rolling resistance characteristics of each vehicle-trailer combination, eliminating the need for complex real-time measurements during normal driving.
Solution Approach 2:
The vehicle itself serves as the measurement instrument by utilizing its own motion and sensor systems to determine its resistance characteristics. The coast-down test uses the vehicle's natural deceleration under its own weight and resistance forces, requiring no external testing equipment or additional complex measurement systems.
2Measurement precision
If coast-down tests are performed to determine vehicle-specific resistance constants, then measurement precision improves, but loss of time and productivity decrease due to additional testing requirements
Solution Approach 1:
The coast-down test is performed as a preliminary one-time operation when the trailer is first coupled to the vehicle or when resistance characteristics are expected to change. This preliminary determination establishes accurate constants for all subsequent operations, eliminating the need for repeated testing and minimizing time loss to a single initial test rather than continuous measurement requirements.
3Reliability
If vehicle-specific resistance constants are determined for each trailer combination, then reliability of brake settings and performance control improves, but device complexity and difficulty of operation increase due to multiple testing procedures
Solution Approach 1:
The vehicle's existing sensor systems and control units perform the resistance determination automatically without requiring manual intervention or specialized testing equipment. The system self-calibrates by utilizing its own motion data and sensor measurements during the coast-down test, making the process as easy as normal vehicle operation while achieving high reliability.
Solution Approach 2:
The system uses feedback from the vehicle's sensor systems (speed, acceleration, brake status) to automatically determine resistance constants and adjust control parameters. This closed-loop approach ensures reliable brake settings and performance control while automating the process to maintain ease of operation, requiring no manual adjustment or complex user procedures.
Data Source
AI summary
Methods and systems determine resistance related constants for use by a vehicle towing a trailer. A system for controlling functions of the vehicle and the trailer includes sensors that provide sensor data. A processor performs a readiness check, based on the sensor data, by determining whether the sensor data exceeds predetermined thresholds. When the readiness check is passed, meaning the thresholds are not exceeded, and based on the sensor data, the processor computes values for constants that represent aerodynamic resistance and rolling resistance of the vehicle and the trailer. Based on the constants, the processor controls functions of the vehicle.